diff --git a/src/auth/src/user_provider.rs b/src/auth/src/user_provider.rs
index e27c2a28a9..03ec034f3a 100644
--- a/src/auth/src/user_provider.rs
+++ b/src/auth/src/user_provider.rs
@@ -65,7 +65,7 @@ fn load_credential_from_file(filepath: &str) -> Result<HashMap<String, Vec<u8>>>
     ensure!(
         path.exists() && path.is_file(),
         InvalidConfigSnafu {
-            value: filepath.to_string(),
+            value: filepath,
             msg: "UserProvider file must be a valid file path",
         }
     );
@@ -86,7 +86,7 @@ fn load_credential_from_file(filepath: &str) -> Result<HashMap<String, Vec<u8>>>
     ensure!(
         !credential.is_empty(),
         InvalidConfigSnafu {
-            value: filepath.to_string(),
+            value: filepath,
             msg: "UserProvider's file must contains at least one valid credential",
         }
     );
diff --git a/src/auth/src/user_provider/watch_file_user_provider.rs b/src/auth/src/user_provider/watch_file_user_provider.rs
index 6e67603597..d268cb51b6 100644
--- a/src/auth/src/user_provider/watch_file_user_provider.rs
+++ b/src/auth/src/user_provider/watch_file_user_provider.rs
@@ -30,6 +30,7 @@ use crate::{Identity, Password, UserInfoRef, UserProvider};
 
 pub(crate) const WATCH_FILE_USER_PROVIDER: &str = "watch_file_user_provider";
 
+/// A user provider that reads user credential from a file and watches the file for changes.
 pub(crate) struct WatchFileUserProvider {
     users: Arc<Mutex<HashMap<String, Vec<u8>>>>,
 }